An ink-jet recording apparatus functions by allowing ink to adhere to a recording material, such as recording paper, by means of an ink discharge method. One example is a thermal method, which generates bubbles and pressure by rapid heating, and then discharges fine droplets of the ink from a fine nozzle. Another example is a piezoelectric method, which discharges fine droplets of ink using a piezoelectric element.
In an ink-jet recording apparatus, rubber members usually are used in ink flow passages containing an ink tank or an ink-jet head. Common examples of such rubber members include a cap for covering an ink head nozzle, a wiper for cleaning an end face of an ink head nozzle, a seal packing to be pinched between parts at a juncture, and a tube for supplying the ink from the ink tank to an ink-jet head.
A rubber base polymer usually is used in the rubber members, such as an ethylene-propylene diene rubber polymer (EPDM) or an isobutylene-isoprene rubber polymer (IIR). The rubber members usually are formed by compounding the non-crosslinked rubber base polymer with one or more additives such as a vulcanization agent, a vulcanization accelerator, a lubricant, a softening agent, a filler, and the like. This rubber composition is then molded into the rubber members using conventional techniques.
When conventional rubber members come into contact with the ink used in the ink-jet recording or a preservative solution filled in the ink flow passage at the time of shipping or storage, an additive contained in the rubber member can be eluted into the ink or the preservative solution. The eluted additive can be deposited as insoluble matter, thereby causing clogging of the nozzle of the ink-jet head or the like.
One effort to address this problem is disclosed in U.S. Publication No. 2005/0116984 A1, which provides a method in which the rubber member is dipped in water at 60° C. in a hermetically-sealed container for a predetermined period of time. The amount of eluted material is measured, so that rubber materials that elute lower amounts of insoluble matter can be identified.
The type or amount of insoluble matter precipitated by an ink or a preservative solution may vary depending on such factors as the composition of the ink or preservative solution. Even when a rubber material selected by the method described in U.S. Publication No. 2005/0116984 A1 is used in the rubber member, insoluble matter still may be eluted from the rubber member. This can happen, for example, when an ink composition is adjusted to have preferable dynamic surface tension from the standpoint of discharge stability, or a preservative solution composition is adjusted to have a preferable dynamic surface tension from the standpoint of a wetting property or ease of replacement with the ink.